The long-term objectives of this proposal are to understand the molecular mechanisms that regulate expression of the human heme oxygenase-1 (HO-1) gene in acute kidney injury. HO-1 is a key regulator of several important biological processes due to the anti-oxidant, anti-inflammatory and anti-apoptotic effects of its reaction products, namely carbon monoxide and biliverdin/bilirubin. Induction of HO-1 is an adaptive and protective response in acute kidney injury following ischemia-reperfusion, nephrotoxins, transplantation, acute glomerulonephritis and rhabdomyolysis as well as several non-renal settings of injury. During the current project period, we have characterized a novel intronic enhancer in the human HO-1 gene that, in conjunction with critical regulatory sites in the promoter, regulates gene expression by heme and nitric oxide, two major stimuli that are implicated in the pathophysiology of acute kidney injury. The transcription factors belonging to the Jun family and upstream stimulatory factor associate with the HO-1 promoter and mutations of the DNA-protein contact points in the HO-1 promoter significantly decrease enhancer function. The hypothesis of this renewal application is that heme oxygenase-1 induction in renal epithelial cells is a protective response in acute kidney injury and occurs through interaction of an intronic enhancer with promoter elements in the human HO-1 gene. In Aim 1, the location and level of HO-1 that is protective in acute kidney injury will be determined by both in vitro and in vivo approaches. In Aim 2, the interaction between the internal enhancer and regulatory sequences in the HO-1 promoter will be examined using the 3C (Chromosome Conformation Capture) and chromatin immunoprecipitation assays. In Aim 3, DNA-protein interactions will be tested in models of acute kidney injury in vivo in luciferase reporter mice driven by human HO-1 promoter/enhancer constructs. By understanding the molecular mechanism(s) that underlies the activation of the human HO-1 gene, we plan to develop specific molecular reagents to manipulate endogenous HO-1 gene expression and exploit its protective effects in renal pathophysiologic states. These studies will also be applicable to other disease settings such as atherosclerosis, sepsis and transplant rejection wherein HO-1 plays an important protective role. PUBLIC HEALTH RELEVANCE The goals of this proposal are to understand the molecular mechanisms that regulate expression of the human heme oxygenase-1 gene in acute kidney injury. The results of these studies will also be applicable to other disease settings such as atherosclerosis, sepsis and transplant rejection wherein heme oxygenase-1 plays an important protective role.